A high strength and toughness and thickness of low alloy hardened and tempered steel and preparation method

A high strength and low alloy steel and quenched preparation toughness and thickness, a low alloy steel technical field. Chemical composition by weight percent, C: 0.13% ~ 0.17%; Si: 0.15% ~ 0.40%; Mn: 1.20% ~ 1.40%; Cr: 0.40% ~ 0.60%; Mo: 0.30% ~ 0.40%; Ni: 0.20 % ~ 0.40%; B: 0.0010% ~ 0.0030%; Nb: 0.015% ~ 0.035%; V: 0.035% ~ 0.060%; Ti: 0.010% ~ 0.020%; Alt: 0.020% ~ 0.040%; P: 0.005% ~ 0.010%; S: 0.002 ~ 0.0050%; carbon equivalent Ceq: 0.54 ~ 0.60; balance being Fe and unavoidable impurities. Advantages: excellent mechanical properties, the mechanical properties of the steel sheet thickness direction of the small and uniform difference; steel sheet excellent internal quality, defect-free detection.